A geometric factor calculation method based on the isotropic flux assumption

One of the instruments onboard the China Seismic Electromagnetic Satellite （CSES） is the Low Energy Particle Detector （LEPD）. The primary objective of LEPD is to provide measurements of the fluxes, energy spectra and pitch angles of 100 keV to 10 MeV electrons and protons from 2 to 50 MeV in the Earth＇s magnetosphere. The geometric factor is one of the principle parameters of a detector, which converts the physical quantity-count rate to the particle quantity-flux. In this paper, we calculated the geometric factor of LEPD via computer modeling of an isotropic radiation environment. It was first demonstrated that the radiation intensity related should obey a cosine-law, then a general sampling method of generating this distribution via GPS of GEANT4 was explained. Furthermore, combined with flux normalization, a comparison of the geometric factor calculation of a set of 2-layer detectors with different shapes （cylinder, truncated cone and rectangle） was performed. Results show a generally good agreement between simulation and analytical calculations for the cylinder and truncated cone detectors, and the result of the rectangular one, for which there is no accurate analytical formula, is consistent with the previous simulated results by others. As a practical instance of the 2-layer rectangle detector, the geometric factor of LEPD is 10.336±0.036 m cm2·sr for 10 MeV proton and 8.211±0.032 m cm2·sr for 8 MeV electron.     

一种奇异的衰变方式

介绍了一种奇异衰变方式即β－延发裂变的基本过程,指出了研究的意义和世界上研究的进展情况。     

新重丰中子同位素^238Th

利用兰州重离子加速器（ＨＩＲＦＬ）所提供的６０ＭｅＶ／ｕ的＾１８Ｏ离子束照射天然铀靶,通过多核子转移反应生成＾２３８Ｔｈ,由快速放射化学分离技术从铀及其反应产物的合物中分离出钍。使用２台高纯锗（ＨＰＧｅ）探测器对样品的γ（Ｘ）活性进行测量,观测到了＾２３８Ｔｈ的β－衰变子本＾２３８Ｐａ的６３５．０ｋｅＶ和１０６０．５ｋｅＶ２条γ射线峰的增长、衰变行为,利用分析递次衰变的计算机程序对其后一条进行了拟     

新重丰中子同位素238Th

利用兰州重离子加速器(HIRFL)所提供的60MeV/u的¹⁸O离子束照射天然铀靶,通过多核子转移反应生成²³⁸Th.由快速放射化学分离技术从铀及其反应产物的混合物中分离出钍.使用2台高纯锗(HPGe)探测器对样品的γ(X)活性进行测量,观测到了²³⁸Th的β^－衰变子体²³⁸Pa的635.0keV和1060.5keV2条γ射线峰的增长、衰变行为.利用分析递次衰变的计算机程序对其后一条进行了拟合,得到母、子体半衰期分别为(9.4±2.0)min和(2.1±0.4)min,二者分别与预言值和文献值相符.另外,在由²³⁸Pa的X射线开门的γ谱中,发现一条能量为89.0keV的新γ射线,经计算,其半衰期为(8.9±1.5)min,由跃迁能量和半衰期的关系认定该射线来源于²³⁸Th的β–衰变.从而证明本实验合成和鉴别了重丰中子新核素²³⁸Th,并测定它的半衰期为(9.4±2.0)min.     

重丰中子新同位素——238Th

利用兰州重离子加速器（ＨＩＲＦＬ）提供的６０ＭｅＶ／ｕ的１８Ｏ离子束照射天然铀靶,通过多核子转移反应生成２３８Ｔｈ．用快速放射化学分离技术从铀及其反应产物的混合物中分离出Ｔｈ同位素．使用两台高纯锗（ＨＰＧｅ）探测器测量了样品的γ射线活性,观测到了２３８Ｔｈ的β－衰变子体２３８Ｐａ的γ射线的生长、衰变行为,测定２３８Ｔｈ的半衰期为9.4±2.0min A new nuclide 238Th has been produced via multinucleon transfer reaction by 60 MeV/u 18 O ion irradiation of natural uranium. The produced thorium was radiochemically separated from the mixture of uranium and its reaction products. The activity of thorium was measured by using a HPGe detector and a planar HPGe detector. 238 Th has been identified for the first time by measuring the growth and decay of the γ rays from its daughter nucleus 238 Pa.     

奇异反应和元素分离

14MeV中子可以引起重核奇异的(n,2p)反应。中能较轻的重离子轰击重核,可以产生多核子转移反应,并以此为基础形成了我们合成和研究重丰中子新核素的一条物理思想和生成、分离鉴别技术路线。介绍了化学分离和X-γ符合方法(元素分离方法);先后合成了一些如185Hf、186Hf、237Th、238Th、239Pa、175Er和197Os等重丰中子新核素,并测定它们的半衰期分别为3.5min、2.6min、5.0min、9.4min、106min、2.8min和1.2min;还观测了它们其他的衰变性质,如新γ射线和衰变纲图等。     

磷酸三丁脂萃取Pa(V)的研究

以TBP（磷酸三丁脂）为萃取剂,苯为稀释剂,以^233pa为示踪剂,研究盐酸溶液中Pa（V）的萃取行为。讨论了盐酸浓度、萃取剂浓度对Pa（V）萃取的影响。同时萃取时间对萃取的影响也进行了讨论。     

三-((2-(N,N-二乙基乙酰胺基)氧基)乙基)胺萃取Th的研究

以三-((2-(N,N-二乙基乙酰胺基)氧基)乙基)胺为萃取剂,1,2-二氯乙烷为稀释剂,研究从硝酸一苦味酸溶液中Th(Ⅳ)的萃取行为。讨论了水相中苦味酸根浓度、萃取剂浓度对Th(Ⅳ)分配比的影响,也对萃取机理进行了初步探讨。     

Gamma decay of the lowly excited states of 189Re

¹⁸⁹W activities were produced via the ¹⁹²Os(n, α) reaction using irradiation of isotopically enriched ¹⁹²Os metallic powder of ~100 mg/cm² with 14 MeV neutrons. The X-γ and γ-γ coincidence measurements were made so as to obtain γ rays from ¹⁸⁹W decay and its coincidence relations. A new simple decay scheme of ¹⁸⁹W including three γ rays of 210.2, 229.6 and 260.2 keV is proposed. Two new levels of ¹⁸⁹Re at 470.4 and 489.8 keV are assigned.     

H型群内上半空间Hardy不等式的最佳常数问题

本文研究了H型幂零李群上Hardy不等式的问题.利用基本解的方法,获得了相关李群上的Hardy不等式,并且所得到的相关Hardy常数是最佳的.